Study On The Characteristics And Sources Of Volatile Organic Compounds And Ozone In Lianyungang City

In recent years,the concentration of atmospheric particulate matter in Lianyungang City had decreased and the concentration of ozone had increased,which had a significant impact on air quality.Volatile organic compounds were important precursors of ozone and so on.In order to study the pollution characteristics and sources of volatile organic compounds and ozone in Lianyungang City,in this paper the data analysis method was used to analyze the ozone historical data and VOCs sampling data,the Positive Matrix Factorization(PMF)method was used to analyze the VOCs sources,the zero dimension box model was used to draw the ozone ekma curve to study the ozone sensitivity,and the three-dimensional model CMAQ-ISAM was used to analyze the ozone sources.The main findings were as follows:First,the characteristics of ozone pollution in Lianyungang City and its relationship with precursors and meteorological conditions were studied.The average daily maximum 8-hour ozone concentration in Lianyungang City in2016-2019 was increasing year by year,reaching 119.25μg/m~3 in 2019,of which the maximum value was 268.25μg/m~3;The number of days of ozone exceeding the standard was increasing year by year.Among them,the ozone level of Hugou Management Station exceeded 50 days in 2019,an increase of 150%over 2016.The seasonal changes in the daily maximum 8-hour ozone concentration during 2016-2019was similar,and generally with peaks in spring and autumn.Ozone in Lianyungang City had a certain negative correlation with NO_xconcentration,a weak positive correlation with VOCs concentration,a high positive correlation with temperature,and a weak negative correlation with humidity.When the prevailing wind direction was northeast and southeast,Lianyungang often had high ozone concentration.Secondly,the characteristics and sources of VOCs components in Lianyungang City were studied.Sampling analysis showed that the VOCs concentration in typical days was 27.46～40.52 ppbv in spring,45.79～53.45 ppbv in summer and 38.84～46.66 ppbv in autumn;the concentration of oxygenated compounds was 41%～48%,which was the highest in all seasons.The species with higher concentration levels were acetone,acrolein,and propionaldehyde.The concentration of isoprene was higher in summer;in general,the concentration of VOCs at 09:00 was higher than that at 13:00,of which the concentrations of acrolein,ethylene and methylene chloride varied greatly between in the morning and in the afternoon;oxygenates had the highest ozone formation potential(OFP),followed by aromatic hydrocarbons and olefins,with the smallest alkane.The species of VOCs with higher OFP were acrolein,propylene and ethylene.The main sources of VOCs affecting Lianyungang City were industrial sources(49%),solvent usage sources(23%),transportation sources(14%),paint usage sources(10%)and natural sources(4%).Finally,the ozone sensitivity and source contribution of Lianyungang City were studied.Ozone formation in Lianyungang City was mainly controlled by VOCs.The VOCs/NO_x ratio in the NO_x control area or VOCs control area was determined to be 3.03 in spring,5.83 in summer,and 5.77 in autumn.Numerical experiments showed that reducing both NO_xand VOCs emission sources was effective in reducing ozone concentration in Lianyungang.When NO_x and VOCs emissions were reduced by 25～75%,the maximum ozone concentration could be reduced by 10～30μg/m~3when the ozone concentration was reduced,and Ozone concentration could be reduced by up to 27.23%.The source analysis results of ozone in late spring and early summer of Lianyungang City in 2019 showed that industry,power plants and residential sources were the main contributing sources,with contributions of 70%,19%and 8%,respectively.Lianyungang City contributed 18%locally;Linyi City and Rizhao City were the main cities that affected the ozone concentration in Lianyungang City,and the contribution rates were 13%and 9%,respectively,and the regional transmission contribution reached 35%.This article took volatile organic compounds and ozone in Lianyungang City as the research objects,and analyzed the observation data to find that the seasonal change of ozone peaks in spring and autumn and the daily change peaks around 15:00;Combining the VOCs component concentration and ozone formation potential,we suggest focusing on oxygenated compounds and olefins;VOCs were mainly derived from industrial production,painting/solvent usage and transportation sources,which together contributed 86%to VOCs.We suggest focusing on controlling the above three types of emission sources.Carrying out collaborative control of NO_x and VOCs and carrying out cross-regional joint prevention and joint control would help improve the ozone pollution situation in Lianyungang City.